The company completed construction of three acid storage tanks in July with capacity of 7,500 tonnes and a new acid unloading facility.
"The pure sulphuric acid in these tanks is diluted down to a weak sulphuric acid mining solution via the new acid handling and delivery system. This weaker acid solution is used in the wellfield operations to leach the copper from the naturally fractured rocks below ground," said COO Roland Goodgame in a statement.
Gunnison, the first new copper project to be fully permitted in the US in over a decade, is an insitu recovery copper extraction project permitted to produce 125 million pounds a year of copper cathode
Triple Flag Mining Finance provided a US$75 million funding package to build the mine comprising a $65 million copper stream and a $10 million private placement.
Shares in Excelsior Mining (TSX:MIN) are trading at C94¢, valuing the company at $222.4 million.